1. Field of the Invention
This invention relates generally to blow molded containers. In particular, this invention relates to such of those containers wherein the so called bumper roll or transfer ring is formed in the blow molding process and mold assemblies for such containers.
2. Description of Related Art
Blow molding is a cyclic process wherein a hollow tubular preform of material in a moldable condition is centered on the parting plane of a mold assembly, the mold assembly is closed around the preform, the preform is expanded so the exterior of the preform abuts molding surfaces defined by the closed mold assembly, the blow molded article is conditioned to be sufficiently rigid to retain its size and shape while unsupported, the mold assembly is opened and the blow molded article is removed. In general, the moldable condition of the preform is achieved when the material of the preform is at an elevated temperature, and the rigid condition of the blow molded article is achieved when the temperature of the material has been reduced. A blow molding machine comprises a press for opening and closing the mold assembly and blowing means for introducing a pressurized fluid (typically air) to expand the preform in the mold assembly. One type of blow molding equipment produces blow molded containers from tubular extrusions produced by extruding equipment arranged relative a molding assembly to position one or more extrusions in the parting plane of the mold assembly. Additionally, blow molding machines may comprise means for handling the molded article upon removal from the mold assembly and means for trimming waste from the molded article (single-stage machines only). Hence, it is known to produce containers having features for facilitating manipulation thereof for removal from mold assemblies and conveyance for subsequent operations.
Blow molding is commonly used for production of containers for transporting, storing and dispensing liquids wherein the blow molded article comprises a body portion comprising a closed end and a neck connecting the container body with a mouth opening for filling the container and dispensing the contents therefrom. Advantageously, the neck portion of the container comprises an exterior surface having a feature, such as a thread, referred to herein as the “neck finish”, for engaging a separable closure for covering the mouth. In addition, the neck portion further comprises an element referred to herein as a “transfer ring” or “bumper roll” for facilitating manipulation of the blow molded article. Mold assemblies for blow molding containers comprise mating mold components wherein molding surfaces open to the mating faces of the mold components define the exterior of the container. Advantageously, mold assemblies comprise replaceable inserts for forming the neck portion, the inserts defining the exterior surface of both the neck finish and the transfer ring. Replacement of such inserts permits production of containers having a different neck finish or to refurbish inserts that are degraded through use.
To broaden the range of containers for which a particular grasping device is suitable, it is desirable to provide transfer rings of large diameter relative to the container body. To insure complete conformance of the preform with the molding surfaces defining the outside diameter of such transfer rings, the height of the transfer rings must be relatively large. Consequently, there is an increased potential for unacceptable deformation at the junction of the transfer ring and neck portion when the container is subjected to compressive loads, as may occur in stacking of filled containers.